Is body mass index sensitively related to socio-economic status and to economic adjustment? A case study from the Congo.

Several nutritional surveys based on representative samples from various urban and rural situations show that the Congo presents a situation of nutritional transition. There is a large prevalence of low body mass index (BMI) in adults from rural zones and this increases with age. There is, however, a large prevalence of high BMI in urban populations despite the persistence of some degree of chronic energy deficiency (CED), particularly at younger ages. Correspondence analysis and logistic regression were used to construct a socio-economic index and measure adjusted risk factors for CED. In rural areas, the major risk factors were old age, sex (women) and the absence of schooling; low economic status, a commonly shared factor, did not differentiate between households for CED. In Brazzaville, CED was linked to a young age (< 30 years) and, clearly, to poverty. The change in the prevalence of CED in mothers from the capital city during a period of economic adjustment showed an increased incidence in young mothers, and also showed that the disparity between low and high economic levels regarding CED had grown. Finally, there was a high level of correspondence between the mean values for the weight-for-height of children and the BMI categories of the mothers. There is a parallel evolution during the period of economic adjustment between the increase of wasting in infants and the increase of CED in mothers. Therefore BMI appears to be a potential core indicator for use in nutritional surveillance in the Congo.